Hepatic Tumor Microenvironments and Effects on NK Cell Phenotype and Function

• Main Authors: Julián Piñeiro Fernández, Kimberly A. Luddy, Cathal Harmon, Cliona O’Farrelly
• Format: Article
• Language: English
• Published: MDPI AG 2019-08-01
• Series: International Journal of Molecular Sciences
• Subjects: liver; NK cells; colorectal cancer; colorectal liver metastasis; tumor microenvironment; exhaustion; hypoxia; lactic acid; adenosine; tryptophan; immune checkpoints; hepatocellular carcinoma; immunometabolism
• Online Access: https://www.mdpi.com/1422-0067/20/17/4131

The liver is a complex organ with critical physiological functions including metabolism, glucose storage, and drug detoxification. Its unique immune profile with large numbers of cytotoxic CD8⁺ T cells and significant innate lymphoid population, including natural killer cells, <inline-formula> <math display="inline"> <semantics> <mrow> <mi>&#947;</mi> <mi>&#948;</mi> </mrow> </semantics> </math> </inline-formula> T cells, MAIT cells, and iNKTcells, suggests an important anti-tumor surveillance role. Despite significant immune surveillance in the liver, in particular large NK cell populations, hepatic cell carcinoma (HCC) is a relatively common outcome of chronic liver infection or inflammation. The liver is also the second most common site of metastatic disease. This discordance suggests immune suppression by the environments of primary and secondary liver cancers. Classic tumor microenvironments (TME) are poorly perfused, leading to accumulation of tumor cell metabolites, diminished O₂, and decreased nutrient levels, all of which impact immune cell phenotype and function. Here, we focus on changes in the liver microenvironment associated with tumor presence and how they affect NK function and phenotype.